ocadaruma

As far as read the blog post, I understand that it assumes the scenario that "a replica dies (and loses its log prefix due to no fcyns) and came back instantaneously (before another replica catches up to the leader)".

Then, in Kafka, what if the leader dies with power failure and came back instantaneously?

i.e.: - There are 3 replicas A(L), B(F), C(F) (L = leader, F = follower) - 1) append a message to A - 2) B, C replicas the message. The message is committed - 3) A dies and came back instantaneously before zk.session.timeout elapsed (i.e. no leadership failover happens), with losing its log prefix due to no fsync

Then B, C truncates the log and the committed message could be lost? Or is there any additional safety mechanism for this scenario?

1) KRaft is only for metadata replication, and data replication is done in ISR based even in KRaft, so it doesn't change the conclusion